Observations on the cabbage stem flea beetle, Psylliodes chrysocephala, on winter oil-seed rape in Cambridgeshire


Alford, DV.

Annals of Applied Biology 93(2): 117-123

1979


The biology of the cabbage stem flea beetle, P. chrysocephala (L.) (Coleoptera: Chrysomelidae), on winter oil-seed rape crops was studied in Cambridgeshire from 1974-1978, with particular reference to autumn and winter activity. The timing of adult invasion of crops in the autumn and subsequent attack on plants by larvae showed considerable variation from year to year, being influenced mainly by temperature. Early-germinating crops tended to be invaded earlier than later-germinating ones. Egg development, closely correlated with temperature, required an accumulated sum of 240 day .degree. C above 3.2.degree. C (calculated from daily mean temperatures). Monitoring adult activity and consideration of temperature data allowed dates of egg hatch to be predicted. Usefulness of this information for accurately timing chemical sprays against the pest is discussed.

Ann.
appl.
Biol.
(1979).
93,117-123
117
Printed
in
Great
Britain
Observations
on
the
cabbage
stem
flea
beetle,
Psylliodes
chrysocephala,
on
winter
oil-seed
rape
in
Cambridgeshire
BY
D.
V.
ALFORD
Agricultural
Development
and
Advisory
Service,
Brooklands
Avenue,
Cambridge,
CB2
2DR
(Accepted
25
June
1979)
SUMMARY
The
biology
of
the
cabbage
stem
flea
beetle,
Psylliodes
chrysocephala
(L.)
(Coleoptera:
Chrysomelidae),
on
winter
oil-seed
rape
crops
was
studied
in
Cambridgeshire
from
1974
to
1978,
with
particular
reference
to
autumn
and
winter
activity.
The
timing
of
adult
invasion
of
crops
in
the
autumn
and
subsequent
attack
on
plants
by
larvae
showed
considerable
variation
from
year
to
year,
being
influenced
mainly
by
temperature.
Also,
early-germinating
crops
tended
to
be
invaded
earlier
than
later-germinating
ones.
Egg
development,
which
was
closely
correlated
with
temperature,
required
an
accumulated
sum
of
240
day
°C
above
3.2
°C
(calculated
from
daily
mean
temperatures).
Monitoring
adult
activity,
and
consideration
of
temperature
data,
allowed
dates
of
egg
hatch
to
be
predicted.
The
usefulness
of
this
information
for
accurately
timing
chemical
sprays
against
the
pest
is
discussed.
INTRODUCTION
The
cabbage
stem
flea
beetle,
Psylliodes
chrysocephala
(L.)
(Coleoptera:
Chrysomelidae),
is
locally
important
in
England
as
a
pest
of
winter
oil-seed
rape
(Alford
&
Gould,
1975).
Extensive
studies
have
been
made
of
its
biology
on
rape
crops
in
France
(Bonnemaison
&
Jourdheuil,
1955),
Hungary
(Saringer,
1967).
Sweden
(Ebbe-Nyman,
1952)
and
Western
Germany
(Kaufmann,
1941;
Buhl,
1959;
Weigand
&
Wendland,
1962)
but,
apart
from
work
on
brassica
seed
crops
in
East
Anglia
during
the
early
1950s
(Williams
&
Carden,
1961),
little
has
been
published
in
England.
In
the
mid-1970s,
several
attacks
of
P.
chrysocephala
were
discovered
on
winter
oil-seed
rape
crops
near
Huntingdon,
Huntingdonshire
(now
included
in
the
administrative
county
of
Cambridgeshire)
and,
as
the
pest
appeared
a
potentially
serious
threat
to
rape-growing
in
the
area,
investigations
were
begun
of
its
bionomics
and
control.
Results
of
some
chemical
trials
have
already
been
published
(Alford,
1977).
The
present
paper
describes
observations
made
on
the
pest
from
1974
to
1978,
with
particular
reference
to
the
period
of
crop
invasion
in
autumn
and
winter.
MATERIALS
AND
METHODS
Field
studies
were
centred
on
farms
approximately
10-20
km
NW
by
W
of
Cambridge
in
an
area
bounded
by
the
A45
and
A604
trunk
roads.
Most
collections
of
adults
were
made
during
the
autumn
and
early
winter,
wherever
possible
at
weekly
intervals,
using
a
sweep
net
(1975
only),
a
D-Vac
insect-collecting
suction
machine
(1976-7)
and
sticky
traps
(1976-8).
Each
trap,
coated
with
Boltac
grease,
consisted
of
a
white,
rectangular
plate
(c.
25
x
15
cm)
and
was
placed
flat
on
the
ground,
sticky
side
upwards.
Four
traps
were
set
in
line,
about
15
m
apart,
the
total
trap
area/station
being
c.
0.15
m=.
Insects
and
debris
were
removed
at
each
examination;
traps
were
replaced
or
re-greased
when
necessary.
Sweep
net,
suction
machine
and
sticky-trap
samples
were
obtained
from
alongside
or
within
fields
which
grew
rape
during
the
previous
118
D.
V.
ALFORD
summer,
and
alongside
or
c.
50
m
into
recently
drilled
or
emerged
rape
crops.
Whole
plants
(less
roots)
were
examined
throughout
the
autumn
and
winter
months
and
live
and
dead
larvae
recorded.
In
1977-8,
data
were
obtained
for
the
whole
period
of
plant
invasion.
Meteorological
data
were
obtained
from
the Wyton
RAF
weather
centre,
10
km
north
of
the
main
study
area.
Laboratory
cultures
of
adults
and
immature
stages
were
kept
in
clear
plastic
sandwich
boxes
and
provided
regularly
with
fresh
oil-seed
rape
foliage.
Boxes
were
stored
at
room
temperature,
in
constant-temperature
cabinets,
or
in
an
insectary
where
continuous
ambient
temperature
measurements
were
made.
RESULTS
Adult
activity
In
July
each
year,
before
aestivation,
young
adults
were
extremely
numerous
on
rape
stubble.
During
harvest,
they
often
swarmed
over
machinery
and
were
taken
into
store
in
vast
numbers
with
the
seed.
However,
they
did
not
constitute
a
storage
problem
and
quickly
dispersed.
After
harvest,
numbers
in
the
field
soon
dwindled
and
few
beetles
could
be
found.
50
40
30
20
10
0
No.
o
f
in
div
idua
ls
1975-6
A-
--2
Temp
e
ra
ture
(
°C)
9
23
6
20
4
18
1
19
26
Oct.
Nov.
Dec.
Jan.
Feb.
Date
of
sampling
Fig.
1.
Mean
weekly
temperature
(-)
and
mean
number
of
Psylliodes
chrysocephala
adults
(0)
and
larvae/50
plants
(A)
in
four
rape
crops.
In
late
August,
after
aestivation,
adults
began
to
appear
again
at
stubble
sites,
populations
reaching
a
peak
in
early
September
(Fig.
2).
Numbers
then
declined
rapidly,
although
a
few
beetles
could
still
be
caught
around
field
margins
well
into
the
winter.
Immigration
of
adults
into new
crops
was
monitored
for
3
yr.
In
1975,
adult
activity
on
four
crops
reached
a
peak
in
early
October
and
then
declined,
few
individuals
being
found
after
mid-
November
(Fig.
1).
The
situation
in
1976
at
three
farms
was
similar
(Fig.
2).
In
both
years,
dif-
ferences
between
sites
was
slight,
all
crops
germinating
at
about
the
same
time
and
maintaining
similar
rates
of
growth.
In
1977,
an
early-germinating
(emerged
15
September)
and
a
late-
germinating
(emerged
6
October)
crop
were
compared.
A
noticeable
difference
in
growth
at
these
sites
(3
km
apart)
was
apparent
throughout
the
study
period,
plant
height
at
the
latter
lagging
by
about
3
wk.
At
the
'early'
site,
adult
numbers
reached
a
peak
4
wk
earlier
and
also
declined
earlier.
At
both,
however,
adults
continued
to
be
caught
on
sticky
traps
in
small
numbers
throughout
the
winter
and
early
spring
(Fig.
3).
Adult
numbers
on
two
other
crops,
which
germinated
on
6
October
but
subsequently
grew
even
more
slowly
than
the
main
'late'
site,
were
greatest
on
9
November;
neither
of
these
sites
was
heavily
infested.
20
18
16
14
12
10
-
-
8
6
4
2
Temp
e
ra
tu
re
(
°C)
-
o
15
10
5
Temp
era
ture
(
°C)
-
o
Psylliodes
chrysocephala
on
winter
rape
in
Cambridgeshire
119
1976-7
A
'A
--„A__•
40
A
/
0
1 1
1 1
1
1 1
-
1 1 1
1
19
2
16
30
14
28
11
25
9
10
16
24
Aug.
Sep.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Date
of
sampling
Fig.
2.
Mean
weekly
temperature
(
)
and
mean
number
of
Psvlliodes
chrysocephala
adults
at
three
stubble
sites
(0),
and
adults
(lb)
and
larvae/50
plants
(A)
in
three
rape
crops.
160
1977-8
120
80
0
0
40
0
/
0
25
15
29
13
27
10
24
8
22
5
3
23
16
13
Aug.
Sep.
Oct.
Nov.
Dec.
Jan.
Feb.
Mar.
Apr.
Date
of
sampling
Fig.
3.
Mean
weekly
temperature
(
)
and
mean
number
of
Psvlliodes
chrysocephala
adults
(111.
M),
and
larvae/20
plants
(0,
•),
in
an
early-
and
a
late-germinating
rape
crop
respectively.
Oviposition
and
egg
hatch
Females
emerging
from
aestivation
in
late
summer
possessed
undeveloped
ovaries,
but
mature
eggs
were
noted
about
12-14
days
after
beetles
began
feeding
on
rape
foliage.
Also,
adults
collected
at
stubble
sites
after
aestivation
and
then
fed
on
rape
foliage
in
the
laboratory
began
egg
laying
about
2
wk
later.
Egg
development
showed
a
significant
(P
=
0.001)
relationship
with
temperature
(Figs
4
and
5),
eggs
taking
an
average
of
37
days
to
hatch
at
daily
mean
temperatures
of
10
°C
and
70
or
more
days
below
6
°C.
Eggs
kept
at
constant
temperatures
above
6
°C
developed
more
rapidly
No.
o
f
in
div
idua
ls
200
160
120
80
No.
o
f
in
div
idua
ls
120
D.
V.
ALFORD
0-09
Re
c
ip
ro
ca
l
o
f
de
ve
lop
me
n
t
t
ime
0.06
0.03
4
8
12
16
20
Temperature
(°C)
Fig.
4.
Determination
of
threshold
of
development
for
Psylliodes
chrysocephala
eggs.
120
100
80
60
40
20
0
' '
'
6
8
10
12
14
16
18
20
Temperature
(°C)
Fig.
5.
Relationship
between
temperature
and
rate
of
development
of
Psrlliodes
chrysocephala
eggs
at
constant
(0)
and
fluctuating
(0)
temperatures
(the
latter
with
S.D.
indicated).
Table
1.
Duration
of
developmental
period
for
eggs
of
Psylliodes
chrysocephala
kept
at
constant
temperature
Temperature
(°C)
No.
of
eggs
Days
to
hatching
(mean
±
s.E.)
20
5
13.2
+
1.7
15
9
22.9
+
2.7
12
1
28
10
6
35.7
+
1.2
7
1
55
5
21
114.4
+
7.0
Day
s
to
ha
tc
h
ing
Psylliodes
chrysocephala
on
winter
rape
in
Cambridgeshire
121
than
those
at
similar
mean,
but
fluctuating,
temperatures
but not
significantly
so
(Table
1).
Eggs
at
a
constant
5
°C
took
an
average
of
>114
days
to
hatch,
considerably
longer
(P
=
0.001)
than
those
at
fluctuating
temperatures
with
a
mean
of
5
°C.
Constant
temperature
data
indicated
that
egg
development
ceased
at
3.2
°C
(daily
mean
temperature—Fig.
4)
and
that
the
date
of
egg
hatch
corresponded
with
an
accumulated
sum
of
240
day
degrees
above
3.2
°C,
calculated
from
the
date
of
egg
laying.
This
value
was
also
applicable
to
eggs
developing
at
fluctuating
temperatures
(Fig.
5).
In
the
field,
observed
intervals
and
mean
temperatures
from
the
commencement
of
oviposition
(regarded
as
beginning
2
wk
after
the
onset
of
adult
immigration
into
the
crop)
to
egg
hatch
(indicated
by
larval
invasion
of
plants)
were
70
days
and
6.7
°C
in
1975
(Fig.
1);
35
days
and
10.7
°C
in
1976
(Fig.
2);
28
days
and
12.5
°C
(`early'
crop),
56
days
and
8.1
°C
(`late'
crop)
in
1977
(Fig.
3).
When
these
data
were
related
to
the
value
of
240
day
degrees,
derived
from:
daily
maximum
+
daily
minimum
2
they
gave
underestimates
for
egg
development,
but
of
only
1,
3,
2
and
7
days
respectively.
Larval
invasion
of
plants
In
1975-6,
the
number
of
larvae
in
plants
built
up
rapidly
from
mid-December
to
mid-
January,
coinciding
with
a
noticeable
increase
in
temperature
(Fig.
1).
In
1976-7,
larval
invasion
occurred
earlier,
increasing
rapidly
in
late
October
and
early
November
(Fig.
2).
In
both
seasons,
however,
adults
were
present
and
eggs
presumably
laid
at
about
the
same
time.
In
1977-8,
noticeable
larval
invasion
of
plants
at
the
'early'
site
began
in
early
November
but
ceased
in
late
November
as
daily
mean
temperatures
dropped
below
about
5
°C;
plant
invasion
subsequently
recommenced
in
late
February
with
the
return
of
warmer
conditions.
At
the
'late'
site,
some
larval
activity
was
seen
in
December
but
most
plant
invasion
occurred
from
late
February
onwards
(Fig.
3).
Volunteer
rape
plants
on
roadside
verges
or
field
margins
were
often
infested
with
P.
chrysocephala
larvae
soon
after
adults
emerged
from
summer
diapause.
By
autumn,
all
three
larval
instars
could
be
found.
New-season
crop
plants
were
infested
noticeably
later
and,
except
in
mild
seasons,
second-instar
larvae
were
usually
present
in
significant
numbers
only
after
mid
winter;
third-instar
larvae
did
not
normally
appear
until
early
spring.
The
rate
of
larval
development
tended
to
be
more
rapid
in
advanced
crops
(Table
2).
Table
2.
Percentage
of
Psylliodes
chrysocephala
larvae
of
each
instar
in
rape
plants
at
various
times
of
the
season
1977-8
Date
of
crop
germination
Date
of
plant
examination
..
15
September
1977
Instar
A
6
October
1977
Instar
r
----A-----
1
2
3
(
1
2
3
Mid-October
1977
100
0
0 0
0
0
Mid-November
100
0
0
100
0 0
Mid-December
99
1
0
100
0
0
Mid-January
1978
97
3
0
10
0
0
Mid-February
87
13
0
100
0
0
Mid-March
40
55
5
95
5
0
Mid-April
29
60
11
97
3
0
Mid-May
3
53
44
0
88
12
Late
May
0 0
100
0
45
55
Early
June
0
0
0
0
22
78
Late
June
0
0
0 0
0
100
3
2
°C
122
D.
V.
ALFORD
DISCUSSION
Aestivation
by
P.
chrysocephala,
which
lasts
about
a
month
(Ebbe-Nyman,
1952),
usually
ends
from
mid-
to
late-August
onwards
and
adult
emergence
is
favoured
by
high
humidity
(Bonnemaison
&
Jourdheuil,
1955).
However,
onset
of
post-aestivation
activity
is
not
dependent
upon
rainfall
or
damp
conditions,
adults
emerging
in
Cambridgeshire
in
1976
several
days
before
the
long
summer
drought
ended
in
late
August.
During
the
study
period,
the
time
of
adult
invasion
of
new
crops
varied
considerably
from
year
to
year
and,
where
differences
were
apparent
in
the
time
of
crop
germination
and
development,
from
field
to
field
in
the
same
area
and
season.
The
timing
of
plant
invasion
by
neonate
larvae
also
showed
considerable
variation.
Earlier
attacks
in
more
advanced
crops
have
also
been
reported
by
Kaufmann
(1941),
Bonnemaison
&
Jourdheuil
(1955)
and
Williams
&
Carden
(1961).
Ambient
temperatures
inevitably
decline
as
the
autumn
and
early-winter
period
advances
so
that
eggs
laid
in
early-germinating
crops
(generally
invaded
earlier
by
adults)
tend
to
hatch
well
before
those
deposited
in
later-germinating,
later-invaded
ones.
This
exaggerates
site-to-site
variations
in
the
main
period
of
plant
attack
by
young
larvae
and
produces
wide
differences
in
optimum
dates
for
spraying
against
them.
If
the
timing
of
adult
immigration
into
a
crop
is
known,
the
onset
of
plant
infestation
by
larvae
can
be
estimated
by
recording
mean
temperatures
from
2
wk
after
adult
activity
is
detected
(to
allow
for
egg
maturation)
and
using
the
results
to
predict
when
eggs
will
begin
hatching.
The
suggested
thermal
constant
for
egg
development
of
240
day
°C,
above
a
threshold
of
3.2
°C,
fitted
the
observed
field
situation
in
all
three
years
(1975-7).
The
slight
underestimates
obtained
were
of
no
practical
importance
and
greater
accuracy
could
not
be
expected
from
weekly
counts.
Abroad,
gamma-HCH
seed
treatments
have
given
good
control
of
P.
chrysocephala
(Hornig,
1964;
Buhl,
1965;
Steinbrink,
1966)
but
chemical
dose
rates
used
in
Britain
are
too
low
to
provide
adequate
protection
and
supplementary
gamma-HCH
sprays
are
required
(Alford,
1977).
Sprays
against
adults
are
intended
to
prevent
direct
feeding
damage
to
young
plants
and/or
to
reduce
the
incidence
of
egg
laying.
However,
with
peak
activity
of
adults
in
rape
crops
limited
to
a
few
weeks,
spray
timing
is
critical
and
treatments
are
often
applied
too
late
to
be
effective.
Similarly,
sprays
against
larvae
(likely
to
be
most
useful
when
applied
at
about
peak
egg
hatch)
are
frequently
timed
incorrectly.
Observations
in
Cambridgeshire,
and
elsewhere,
suggest
that
spraying
against
adults
can
prevent
excessive
grazing
of
foliage
and
reduce
the
eventual
level
of
larval
attack
but
best
control
of
the
pest
with
gamma-HCH
sprays
is
achieved
by
killing
the
young
larvae
(Bonnemaison
&
Jourdheuil,
1955;
Williams
&
Carden,
1961;
D.
V.
Alford
&
C.
W.
Graham,
unpublished
results).
Monitoring
adults
should
enable
sprays
against
them
(if
required)
to
be
timed
correctly
but,
because
of
more
unpredictable
early-winter
weather
and
field
conditions,
spraying
against
the
larvae
on
or
about
the
date
of
peak
egg
hatch
is
often
impossible.
Also,
the
main
period
of
egg
hatch
can
be
interrupted
and
greatly
delayed
by
the
intervention
of
low
temperatures.
In
Cambridgeshire,
spraying
against
larvae
in
November
is
often
a
suitable
compromise
and
this
sometimes
allows
the
insecticide
to
be
applied
with
a
pre-winter
herbicide.
Where
late-autumn
or
early-winter
treatments
have
been
ineffective
or
could
not
be
applied.
spraying
in
mid
or
late
winter
may
be
necessary
once
weather
conditions
improve
and,
as
indicated
above,
such
sprays
may
coincide
with
the
commencement
or
renewal
of
egg
hatch.
Although
optimum
treatment
dates
will
vary
according
to
weather
conditions
and
the
relative
earliness
or
lateness
of
a
crop,
it
should
be
possible
to
judge
in
any
particular
year
whether
early
or
late
treatments
are
appropriate.
However,
detailed
pest
monitoring
and
consideration
of
ambient
temperatures
should
allow
more
accurate
spray
timing
and
lead
to
better
pest
control.
I
thank
members
of
the
Entomology
Department
at
Cambridge
for
assistance,
particularly
Dr
W.
J.
Jordan,
Miss
H.
M.
Taylor
and
Miss
L.
J.
Baker,
various
farmers
for
allowing
work
to
be
Psylliodes
chrysocephala
on
winter
rape
in
Cambridgeshire
123
done
on
the
land.
Mr
P.
Halfpenny,
Department
of
Applied
Biology.
University
of
Cambridge,
for
loan
of
a
D-Vac
suction
machine,
and
Mr
J.
Cochrane
for
statistical
advice.
REFERENCES
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D.
V.
(1977).
Chemical
control
of
the
cabbage
stem
flea
beetle.
Psvlliodes
chrysocephala,
on
winter
oil-seed
rape.
Annals
of
Applied
Biology
85,369-374.
ALFORD,
D.
V.
&
GOULD,
H.
J.
(1975).
Surveys
of
pest
incidence
on
oil-seed
rape
in
the
UK.
Proceedings
of
the
8th
British
Insecticide
and
Fungicide
Conference
2,
489-495.
BONNEMAISON,
L.
&
JOURDHEUIL,
P.
(1955).
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d'hiver
du
colza
(Psylliodes
chrysocephala
L.).
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des
Epiphvties
5.
345-524.
BUHL,
c.
(1959).
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und
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und
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des
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(Psvlliodes
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L.)
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und
Pflanzenshutz
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321-338.
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c.
(1965).
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des
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(Psylliodes
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L.)
in
einem
geschlossenen
Rapsanbaugebeit
auf
sein
derzeitiges
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fur
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und
Pflanzenshutz
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351-355.
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E.
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H.
(1964).
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305-324.
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G.
(1967).
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10,
135-162.
STEINBRINK,
H.
(1966).
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und
Befall
mit
Larven
des
Rapserdflohes
(Psylliodes
chrysocephala
L.)
am
Winterraps
im
mecklenburgischen
KUstengebiet.
Wissenschaftliche
Zeitschrift
der
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ei
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315-317.
WEIGAND,
G.
&
WENDLAND,
E.
(1962).
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und
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und
Bekampfung
des
Rapserdflohs
in
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landwirtschaftliches
Jahrbuch
39,
965-
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J.
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w.
&
CARDEN,
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W.
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1979)